Iron-base scrap preheating apparatus and method

Abstract

In order to preheat pieces of iron scrap of various sizes and shapes highly effectively while avoiding the fusion of the pieces of iron scrap, a rotary kiln type preheating furnace and a shaft type preheating furnace are arranged in parallel with each other in the front stage of a melting furnace in which iron scrap is melted, and preheated iron scrap is charged from both preheating furnaces into the melting furnace. A damper is provided between the shaft type preheating furnace and the melting furnace, so that exhaust gas discharged from the melting furnace is prevented from directly flowing into the shaft type preheating furnace and introduced into the rotary kiln type preheating furnace. Exhaust gas which has passed through the rotary kiln type preheating furnace is introduced into the shaft type preheating furnace preferably from an upper portion and discharged from a lower portion. The rotary kiln type preheating furnace and/or the shaft type preheating furnace includes an air or oxygen gas introducing port used for burning components contained in the exhaust gas.

What is claimed is: 
     
       1. An apparatus for preheating and melting iron scrap for recycling comprising: a melting furnace for melting the iron scrap and generating an exhaust gas; a preheating device connected to said melting furnace for preheating said iron scrap with said exhaust gas; an exhaust gas treating device connected to said preheating device for treating exhaust gas which has been used for preheating, wherein said preheating device comprises a rotary kiln preheating furnace and shaft preheating furnace, arranged in parallel with each other, connected to first and second openings in said melting furnace and connected to each other; and wherein exhaust gas is discharged from said melting furnace through said first opening into said rotary kiln preheating furnace; exhaust gas discharged from the rotary kiln preheating furnace is introduced into the shaft preheating furnace; and iron scrap is independently charged into and preheated by the rotary kiln preheating furnace and the shaft preheating furnace and then fed into the melting furnace. 
     
     
       2. An apparatus for preheating iron scrap according to claim 1, wherein a damper is arranged in said second opening between the shaft preheating furnace and the melting furnace, and exhaust gas discharged from the melting furnace is prevented from directly flowing into the shaft preheating furnace. 
     
     
       3. An apparatus for preheating iron scrap according to claim 1, wherein exhaust gas which has passed through the rotary kiln preheating furnace is introduced into the shaft preheating furnace from an upper portion and discharged from a lower portion. 
     
     
       4. An apparatus for preheating iron scrap according to any one of claims 1, wherein the shaft preheating furnace includes a pusher type delivery mechanism. 
     
     
       5. An apparatus for preheating iron scrap according to claim 1, wherein the shaft preheating furnace includes a grate opening and closing type delivery mechanism. 
     
     
       6. An apparatus for preheating and melting iron scrap for recycling comprising: a melting furnace for melting the iron scrap and generating an exhaust gas; a preheating device connected said melting furnace for preheating said iron scrap with said exhaust gas; an exhaust gas treating device connected to said preheating device for treating exhaust gas which has been used for preheating; wherein said preheating device comprises a rotary kiln preheating furnace and a shaft preheating furnace, arranged in parallel with each other, connected to first and second openings in said melting furnace and connected to each other; and wherein exhaust gas is discharged from said melting furnace through said first opening into said rotary kiln preheating furnace; exhaust gas discharged from the rotary kiln preheating furnace is introduced into the shaft preheating furnace; and at least one of the rotary kiln preheating furnace and the shaft preheating furnace is provided with an air or oxygen gas introducing port used for burning combustible components contained in exhaust gas so that a combustion ratio in each preheating furnace can be adjusted. 
     
     
       7. A process for preheating and melting iron scrap in which iron scrap is preheated before it is melted in a melting furnace, comprising the steps of: charging iron scrap into both a rotary kiln preheating furnace and a shaft preheating furnace, which are arranged in parallel with each other in a front stage of the melting furnace; charging iron scrap from the rotary kiln preheating furnace and the shaft preheating furnace into the melting furnace, melting iron scrap, and generating exhaust gas in the melting furnace; preventing the exhaust gas, which has been discharged from the melting furnace, from directly flowing into the shaft preheating furnace; introducing the exhaust gas, which has been discharged from the melting furnace, into the rotary kiln preheating furnace; and introducing the exhaust gas, which has passed through the rotary kiln preheating furnace, into the shaft preheating furnace so as to preheat iron scrap. 
     
     
       8. The process for preheating iron scrap according to claim 7, wherein exhaust gas which has passed through the rotary kiln preheating furnace is introduced into the shaft preheating furnace from an upper portion and discharged from a lower portion. 
     
     
       9. A process for preheating iron scrap according to claim 7, wherein air or oxygen gas is introduced into at least one of the rotary kiln preheating furnace and the shaft preheating furnace so that combustible components contained in exhaust gas can be burned while a ratio of combustion in the each preheating furnace is controlled. 
     
     
       10. A process for preheating iron scrap according to any one of claim 7, wherein pieces of iron scrap, the average diameter of which is not more than 300 mm, are charged into the rotary kiln preheating furnace, and pieces of scrap iron, the average diameter of which is not less than 300 mm, are charged into the shaft preheating furnace so as to conduct preheating. 
     
     
       11. A process for preheating iron scrap according to any one of claim 7, wherein the preheating temperature in the rotary kiln preheating furnace is not higher than 1200° C., and the preheating temperature in the shaft preheating furnace is not higher than 800° C.